I have a 1988 k5 blazer with a 350/th400 combo. The engine is bored .030 over, has a bigger cam, roller rockers, and a holley 770 carb. The th400 has a 2500 stall torque converter.

The truck has run and drove perfectly for a little over a year now, just recently I've been getting a stalling problem. After I let the truck get to operating temp I'll put it in drive and it will drive perfectly, the problem is when I stop. If i come to a complete stop and let the truck idle in drive (or reverse) it will idle for about 30-40 seconds then start to bog down and eventually stall. It will start right up again and idle in neutral normally. Put it in gear and it will eventually bog down and stall again.

Like I said this has just recently started happening. I have a bad feeling that the torque converter is to blame but its less than a year old. (I switched from a 4000 stall converter to a 2500 stall converter in june of this year) Plus the th400 is not a lock up converter and I don't hear any noise coming from the trans to indicated a worn or seized bearing.

What about fuel pump? Also check the hei ignition moduale. They have problems and fail all the time if its stock i would replace it. Coil is also a likely suspect as they have a tendencey to crap out every so often. Bad wires and aweak coil rpm fails and spark voltages drops it will drop out.

Does it feel like its pulling or tugging in gear. Also if you flat floor it and ask for max power from a dead stop does it respond as it should. Usally tq converter will not be happy under full throttle launch if the converter is shot.

If the trans is working fine other wise i would not look at it first even if it feels like the trans is holding the engine back. Many times a bad spark plug wire will make and engine seem like the trans is choking it out.

The fuel pump is good, its a newer (6 months) in-tank tbi fuel pump. (truck used to be tbi) I have the pressure regulated to 7psi. I can see in the clear filter that the fuel is good and the fuel gauge shows a strong 7psi

As for the ignition I have a MSD street fire hei distributor and MSD street fire ignition box so i don't have and ignition module anymore. The coil seems to be firing fine, I have a clear distributor cap and can see that all 8 cylinders are getting a nice bright, strong spark. Now I know my wires are not the best, if you look under the hood at night you can see all but 2 cylinders are sparking in the boots at the spark plugs. I haven't gotten around to changing the wires but they've done this for almost a year now and this stalling problem is brand new.

From a dead stop when I floor the engine I break the rear tires loose and it seems to pull fine. I tried doing a stall test in 2wd but as soon as I got to half throttle it would start burning the tires. I retried the stall test in 4wd with all the tires blocked and at full throttle the tach read 2300-2500 so I think the torque converter is working. But when I brake torque with about quarter throttle it bogs down and dies unless I throw it in neutral real quick.

You still need to test the fuel pump. The pressure may look fine at idle but what about under load? You need to disconnect the fuel line from the carb and add a length of hose where you can pump gas into a bucket safely. You may not have enough volume. There could be some small specs of dirt got into the needle and seat in the carburetor. You should have a 40 micron filter before the carb not the cheap glass filters. Did you do away with the factory fuel filter that is on the frame rail on the driver's side.

no I kept the frame mounted fuel filter but It may be original from 1988. I never changed it due to lines being frozen. I may have to bite the bullet and change it. But the fuel looks pretty clean in the glass filter before the carb.

You definetely need to get the old filter removed. This could be what's holding back your fuel volume. Doesn't both lines just screw into the filter? If so use locking pliers to hold the filter and whatever size line wrench to loosen the line nut.

The fuel pump is good, its a newer (6 months) in-tank tbi fuel pump. (truck used to be tbi) I have the pressure regulated to 7psi. I can see in the clear filter that the fuel is good and the fuel gauge shows a strong 7psi

As for the ignition I have a MSD street fire hei distributor and MSD street fire ignition box so i don't have and ignition module anymore. The coil seems to be firing fine, I have a clear distributor cap and can see that all 8 cylinders are getting a nice bright, strong spark. Now I know my wires are not the best, if you look under the hood at night you can see all but 2 cylinders are sparking in the boots at the spark plugs. I haven't gotten around to changing the wires but they've done this for almost a year now and this stalling problem is brand new.

From a dead stop when I floor the engine I break the rear tires loose and it seems to pull fine. I tried doing a stall test in 2wd but as soon as I got to half throttle it would start burning the tires. I retried the stall test in 4wd with all the tires blocked and at full throttle the tach read 2300-2500 so I think the torque converter is working. But when I brake torque with about quarter throttle it bogs down and dies unless I throw it in neutral real quick.

Sorry for the novel.

have you tried to run it at 6 psi 7 is a little low. 5 psi is normal for most carbs but not sure about the holley 770 carb you mentioned.

If it idles fine but falls off at high rpm with 6 psi your regulator may not be able to flow enough to support the carb at max flow. I would check with holley and see what the carb is meant to run at. If its 7 psi then ignore my dribble. LOL

Do you still have the TBI exhuast. is there oem o2 sensor still in place you can buy a lean rich guage pretty cheap and see if the motor is very rich or goes lean when the problem occurs. these just hook up to the stock o2 sensor and read the output. Now the o2 sensor has a small range but can be used for general lean rich condition check.

In a perfect world I should be able to get the old fuel filter off with line wrenches, last time I tried the line itself was frozen to the nut so the line wanted to twist. I'll have to start spraying some wd40 on it a few days before. This weekend I'm going to try to replace that fuel filter and my arching wires. I have some msd 8.5mm wires on order.

as for the fuel pressure on the carb, I'm not actually sure what it should be set at, numerous sources I've found have said between 5 and 7psi. I'll lower the psi to 5 and see if that makes a diffrence but I'm not having a problem at high rpm, the truck runs amazing, it launches off the line, and pulls steady at all rpms, the problem is when I come to a stop and idle in gear for more than 40 seconds, after 40 seconds of idling in gear it will start to sputter and stall but starts right up again on one crank, or I can put it into neutral when it starts to sputter and it will be fine. Also I replaced my exhaust with long tube headers out to 3" true dual pipes to a pair of thrush mufflers with turn downs at the mufflers. The entire tbi system was removed. The computer is collecting dust on a shelf in my garage lol.

I would try it at 5 psi for sure that can be the problem if its flooding over the floats. Not all carbs and fuel pressure regulators will work correctly at max pressure. Best to pull it back some i bet that will help smooth things out a bit.

If it solves the problem but runs lean at wot the regulator needs to be upgraded. Tbi pump should be fine but regulators usaly cost a pretty penny for a good one.

I'll try that, hopefully my regulator is fine, It's a $80 or $90 holley fuel pressure regulator for return style fuel systems. I figure I'd get a holley regulator since its a holley carb. I couldn't run the tbi fuel pump right to the carb since that put out over 15 psi which would most likely set the carb on fire.

well I set the fuel pressure going to the carb at 5psi and no change. But I noticed something and its got me thinking...is there any way that this problem could be caused by cold weather?

Ever since I've had this engine and trans combo I've never driven this truck past mid november. I've always parked it for winters so all tuning was done in summer weather. Last night it was 47 degrees here and the truck would die idling in gear after about 40-50 seconds (at operating temp). tonight it was 36 degrees and after having some trouble starting it at this temp it only idled for about 10-15 seconds in gear (at operating temp). Can cold weather have this effect or am I just being hopeful?

well I set the fuel pressure going to the carb at 5psi and no change. But I noticed something and its got me thinking...is there any way that this problem could be caused by cold weather?

Ever since I've had this engine and trans combo I've never driven this truck past mid november. I've always parked it for winters so all tuning was done in summer weather. Last night it was 47 degrees here and the truck would die idling in gear after about 40-50 seconds (at operating temp). tonight it was 36 degrees and after having some trouble starting it at this temp it only idled for about 10-15 seconds in gear (at operating temp). Can cold weather have this effect or am I just being hopeful?

sure you can try to turn the idle fuel crew out a half to full turn and see if that helps.

Alright so I'm starting to lean towards a possible fuel problem now. Last night I went out and turned the idle fuel screws out a half turn each. started the truck and let it warm to operating temp. I put it in drive and I thought it was fixed. The engine didn't bog down or anything, it ran great. Then like clock work after 60 seconds it sputtered and died quickly, almost with out warning. After that I couldn't get the truck started untill about two minutes later. I'm pretty sure the engine was flooded out.

I let it sit, turned the screws back in a half turn and it started right up again. Could I be looking at a carb problem? It seems like its getting enough fuel if it flooding out. Or do I just need to keep looking for the right idle fuel mixture?

Well the condition seems to be getting worse, now it starting to idle kind of rough in park/neutral too. Tonight I went out to start the truck, let it get to operating temp and like i said it seemed to idle slightly crappy in neutral. I shifted into drive and after 30 seconds or so it sputtered, coughed, and died. but this time when I tried to restart it, it wouldn't start. It just cranked and cranked. I let the truck sit for a little over a minute and then it started right out.

I'm thinking that it flooded out and I'm starting to rule out torque converter. Could this be the sign of a failing coil, sending a weak spark and letting the engine flood out? Any other ideas? Thanks in advance.

The arcing you described seeing at night indicates that the cylinders aren't firing, thus it seems to be flooding out. Also, the more they arc the more the insulation breaks down, taking more of the spark energy away from the plugs.

Poor idle can often be a carb/fuel/pump problem, especially if you're flooding out. If you do have a fuel problem, it's either running rich and you can smell the fuel; or it's running lean and you will notice a burnt smell.

Also, before you replace the fuel pressure regulator, you should check the fuel level in the carb. Your holley has a plug in each fuel bowl, when you remove one (after briefly running the engine) a small amount of fuel should come out.
A lot of fuel coming out indicates that your needle/seat can't hold against the fuel pressure coming in, it (needle/seat) has deteriorated and needs replacement, or the float setting needs adjustment (least likely because it ran good before and the setting shouldn't change, of course the float could be leaking and need replacement).
No fuel coming out means float setting, needle/seat, or fuel pressure is the problem (along the line of previous discussion).

Obligatory WARNING - raw fuel spilling from the carb can catch fire causing serious injury or death, take necessary precautions. Oh and that thing about gasoline and cancer!

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